Taking well YJ1 as the research object, the pore variety of shale oil reservoir of Chang-7 member in Ordos Basin is characterized qualitatively and quantitatively by using scanning electron microscope and high pressure mercury injection technology. The movable fluid in reservoir is researched by using nuclear magnetic resonance technology, and the main controlling factors affecting the difference of reservoir quality are discussed in detail. The results show that the lithology of high-quality shale oil reservoir in Chang-7 member of Ordos Basin is mainly fine-grained?very fine-grained lithic sandstone, and the sedimentary facies are mainly sandy clastic flow deposition. The reservoir pore types include primary intergranular pores and secondary dissolution pores, and the proportion of intergranular pores is more than that of dissolution pores. According to the type of pore variety, the reservoir can be divided into three types, among which the type I reservoir is the most high-quality reservoir in the study area, with good porosity and permeability. The mobility of reservoir fluid in the study area is mainly affected by the properties of pore variety, the mobile fluid is mainly stored in the macropores, and the effective pore volume is the factor restricting the mobility of fluid. The sand body caused by sandy clastic flow in the study area is a necessary condition for the formation of high-quality reservoir. The proportion of skeleton particles and cement in the rock is the key for the change of reservoir properties. When the skeleton particles increase and the cement content decreases, it is easy to form high-quality reservoir.